Registration validity for casual and non resident taxable persons requires advance tax deposit credited to cash ledger and may be extended. Casual taxable persons and non-resident taxable persons must obtain a certificate of registration valid for the period specified or a limited initial term, with a possible administrative extension. They must make an advance deposit of tax at the time of application equal to estimated liability, and where an extension is sought, deposit an additional estimated amount. Deposits are credited to the person's electronic cash ledger and utilized as provided by the law.